The present invention relates to closures for trailers and more particularly to a door-mounted gasket for a comb-type rear frame of a trailer.
A very successful rear frame for vehicles such as trailers is the so-called "comb-style" corner post assembly shown in U.S. Pat. No. 3,564,771, which hereby is incorporated herein by this reference. As shown therein, the geometry of the comb-type frame with its vertical member 6 consisting of an outer rear post 9 and an inner post 10 necessitates the use of a unique hinge that allows the door 5 to seal against the rear frame, as well as allowing the door to swing open around the comb 9 and lay flat against the side wall 3 of the vehicle body or container 1. As explained in this patent, the perimeter inside edges of the rear doors are provided with an EPDM sponge rubber compression style gasket that seals against inner post 10 when door 5 is swung into the closed position.
Another style of door gasket suitable for dry-freight applications is commonly referred to as a "flapper" gasket or a "wiper" gasket. This flapper gasket generally is composed of a dual durometer PVC or vinyl material. It has a channel-shaped hard section of material that acts as a carrier and fastens to the door plaque. Two soft sections of material are attached to the channel and disposed to wipe along the sealing surface of the rear frame. The outer seal lies on the outer surface of the frame and is the primary seal to keep moisture and such from entering the trailer. The inner seal is generally smaller and deforms against the inner sealing areas, thereby providing a barrier to prevent moisture and such from actually entering the cargo area of the trailer. In the space between the two flexible seals, a channel exists for the purpose of trapping moisture or contaminants that may pass by the outer seal and in theory ideally are stopped by the inner seal. Ideally, moisture and contaminants drain through the channel to the bottom, whence they can be expelled by gravity.
Because of the geometry of the comb-style rear post and hinge, existing flapper gasket configurations fail to perform the desired sealing functions. The geometry of the comb-style rear frame (with its unique hinged configuration and location of the hinge pin) causes the doors to approach the corner post sealing surface from more of a lateral direction as opposed to a conventional rear-to-front swing closure. This in turn causes the outer seal to hit the inner post in a manner causing the outer seal to turn inside instead of sliding to the outside to form a moisture barrier.
Thus, a trailer manufacturer desiring to meet a customer preference for a flapper gasket could not use a comb-style frame. While non-comb style rear frames use different style hinges and hinge pin locations that result in operation of the doors in a manner consistent with proper functioning of flapper gaskets, the customer must be willing to forego the advantages of the wrap around hinges and hinge pin location attributable to the comb-style rear frame. If such customer also preferred the advantages accruing to the unique comb-style rear frame and its hinge protective attributes, the manufacturer would be forced to use a so-called "notched" comb-style rear frame. However, since the "notched" comb-style rear frame uses the same style hinge as the non-comb, notches must be provided in the outer post in the region of the hinges to accommodate movement of the hinges when opening and closing the doors. This requires the manufacturer to produce and inventory three different types of outer posts for the rear frames. Moreover, from the manufacturer's perspective, the need to produce and inventory "notched" comb-style rear frames, including the different style hinges, is disadvantageous.